Hydrazine hydrate is obtained by the oxidation of ammonia in the presence of carbonyl compounds by a number of different processes. These processes, which differ in particular by the nature of the oxidizing agent and by the nature of the carbonyl compounds used, make it possible to obtain the hydrazine in the form of stable organic combinations in the reaction medium. By way of illustrating these processes, there are noted especially those described in French Pat. Nos. 2,092,734 and 2,324,618; German Pat. Nos. 1,088,939, 1,103,902, and 1,123,330; British Pat. Nos. 1,122,034 and 1,133,762; U.S. Pat. No. 3,976,756, and Japanese Pat. No. 706532. In a general manner, the hydrazine hydrate is obtained from these combinations by acid hydrolysis or by the sole action of water under determined conditions of temperature and pressure as described, for instance, in French Pat. Nos. 2,323,634 and 2,323,635 or German Pat. Nos. 1,066,558 or 1,130,797. The hydrazine hydrate is obtained in the form of an aqueous solution of a concentration between 1 and 100%; more generally between 5 and 35%.
The nature of the oxidation reactions used cause these processes to generate at the same time as generating the stable organic combination of hydrazine, by-products of various natures, composed of carbon and hydrogen atoms with which oxygen and/or nitrogen atoms can also be associated. They are formed either during the oxidation reaction or during the hydrolysis reaction. Thus, for instance, these dissolved products can be the principal constituents of the oxidation solution; azine, hydrazone, diazacyclopropane, and the like, but also the alkaline condensation products of the carbonyl derivative: ketoalcohols, unsaturated ketones, dihydropyridines, tetrahydropyrimidines, piperidones, and the like, or yet reaction products of the preceding compounds with hydrazine; namely, pyrazolines and the like; and finally products having simultaneously been subjected to several of the preceding chemical transformations. More precisely and without limitation, these are either hydrocarbons or compounds comprising ketone, alcohol, epoxide, amine, amide, oxime, hydrazone, hydrazine, or azine functional groups with the compounds capable of presenting a heterocyclic structure of the pyrazoline, pyrazole, aziridine, pyrazine, pyridazine, triazole, imidazole, pyrrole, or pyridine type, and the like.
These by-products can be encountered again in the hydrazine hydrate solution and in order to purify it, it is necessary to resort to suitable chemical engineering operations such as distillation or liquid-liquid extraction. In this manner, one arrives effectively at lowering the ratio of these by-products down to a value below 1%, and more generally between 0.1% and 0.3%, values below which one cannot descend economically by such means, because of the complexity of the equilibria set in action during these purification operations.
The presence of these impurities can, in a certain number of applications, reveal themselves as undesirable. Amongst others, there is cited the uses of hydrazine hydrate as raw material in the fabrication of medicinal substances or as composing the propellants of special engine motors (airplanes or satellites, for instance).
It is known in the prior art to proceed with the purification of aqueous hydrazine solutions by treatment on ion exchange resins (U.S. Pat. Nos. 3,458,283, 3,652,218, and 3,740,436; and Japanese patent No. 72-45275). But these compounds concern only the elimination of ionic impurities, such as Na.sup.+, Cl.sup.-, and the like of aqueous hydrazine solutions.